The present invention relates to groundwater cleanup, particularly to the destruction of groundwater contaminants by thermal hydrous, pyrolysis/oxidation, and more particular to a thermal treatment wall emplaced to perform in-situ destruction of contaminants in groundwater.
In recent years substantial effort has been directed to the cleanup of underground contamination, particularly groundwater contamination. Various remediation methods have been developed, primarily thermal type remediation techniques wherein heating of the contaminated groundwater, for example, was carried out by electrical heating or by cyclic steam injection to produce an engineered treatment zone. These early efforts primarily involved a pump and treat technology, wherein the contaminated matter was pumped to the surface and then treated. More recently, the development of the microbial filter extended the concept of an engineered treatment zone in the subsurface. Recent efforts also involved the destruction of contaminants by thermal hydrous pyrolysis/oxidation. Also, prior efforts have been directed to the treatment wall concept, and efforts at the Lawrence Livermore National Laboratory have been focused on understanding the key parameters which optimize destruction in the reaction zone, which provides the framework for the present invention involving a thermal treatment wall.
The present invention is a derivative of the prior techniques and provides a thermal treatment wall which incorporates known heating techniques (either electrical or cyclic steam injection), the treatment wall concept, and in-situ destruction of contaminants by thermal hydrous pyrolysis/oxidation. By the combining of these three prior techniques, many common chemical contaminants can be destroyed in-situ by increasing the temperature in the presence of sufficient oxygen or mineral oxidants, which can be injected into the ground if needed.
The present invention initially involved the concept of applying in-situ thermal enhancement in a thermal wall configuration as a plume interdiction method. The initial concept was a planar thermal treatment wall similar in structure to a microbial filter, but utilizing various heating methods including electric resistance heating and steam injection. This initial planar wall concept was expanded to include a thermal treatment zone(s) surrounding pumping well(s). Thus, the invention can be used for both plume interdiction and near-wellhead in-situ groundwater treatment.
In-situ treatment, as used in the present, is a significant step beyond the commonly-used pump and treat technology. Pump and treat systems are primarily used for hydrologic containment of underground contamination, rather than as a contaminant removal method. Since pumping contaminated groundwater rarely removes much contaminant mass (due to the solubility limits of the contaminants in water and their entrapment by capillary forces or by sorption on soil particles), it requires the treatment of many pore volumes of groundwater to clean as aquifer. Once the contaminated fluids are pumped to the surface, treatment and disposal (of both the contaminants and the treated water) are required. There is significant expense in the handling, treatment and disposal of the pumped fluids. With the development of in-situ contaminant destruction techniques, costly ex-situ treatment is not needed.
Thus, the present invention, a thermal treatment wall, can be emplaced to perform in-situ destruction of contaminants in groundwater. Thermal destruction of specific contaminants occurs by hydrous pyrolysis/oxidation at temperatures achievable by existing thermal remediation techniques and in the presence of oxygen or soil mineral oxidants. The invention is particularly useful where applied to dissolved contaminant plumes.